Usually a phenomenon left to the realm of public bathrooms or workplace bathrooms, literally a smear of shit often occuring in unexpected areas such as the floor or the wall, confusing the succeeders of the incident.

There were fresh shit smears on the wall, which may seem a strange observation to make, but he had only just been in the bathroom an hour earlier when the wall was actually just plain white tile, whereas now it had become newly decorated with what he wanted to believe were just strokes of brown paint, but he knew in his heart it was something much more human in origin.